New Jersey Gov. Chris Christie on Thursday appointed state Attorney General Jeffrey Chiesa to temporarily fill the seat held by the late Frank Lautenberg.
Chiesa, a Republican, will hold the seat until a special election, which Christie set for Oct. 16. Chiesa does not plan to run in that election, Christie said.
"I'm perfectly comfortable with that decision," the governor added.
Lautenberg, who served nearly 30 years in the Senate, died Monday. With the selection of his replacement, New Jersey politicians will now focus on the special election as candidates begin to come out of the woodwork.
Rep. Rush Holt became the first Democrat on Thursday to announce he's seeking his party's nomination for the seat. Former Bogota Mayor Steve Lonegan is to announce Thursday that he'll seek the Republican nomination.
Whoever wins will hold the seat until it expires in January 2015. The winner of that election would have to run again in 2014.
In an email Thursday to supporters, Holt explained why he's running. "The reason is simple," he wrote. "I believe I am the best candidate to continue the passionate advocacy for progressive values that Sen. Lautenberg exemplified."
Holt, now 64, was assistant director of the Princeton Plasma Physics Laboratory for most of the 1990s before being elected to Congress in 1998. Around his central New Jersey district, it's not uncommon to see a bumper sticker that proclaims, accurately: "My congressman IS a rocket scientist."
He's considered one of the most liberal members of New Jersey's congressional delegation. He's pushed for laws against racial profiling and has been critical of drilling for oil and natural gas on public lands and waters.
Two well-funded Democrats, U.S. Rep. Frank Pallone and Newark Mayor Cory Booker, had expressed interest in the seat before Lautenberg died, but neither has made an announcement so far. Booker began raising money to seek the seat in January and has brought in about $2 million.
The only Republican in the race so far is Lonegan, a conservative who has twice sought his party's nomination for governor.
Lonegan, who runs the New Jersey office for American for Prosperity, said Wednesday that he looks forward to weighing in on national issues such as the Obama administration's handling of the attack last year at the diplomatic mission in Benghazi, Libya, and the selective scrutiny of conservative groups' nonprofit tax applications.
Christie faced conflicting state laws in deciding when to have the election. He could have waited until November 2014, or possibly this November.
But Christie said Tuesday it was worth the expense to the state to hold a special election earlier.
"The citizens of New Jersey need to have an elected representative to the United States Senate and have it as soon as possible," he said.
With the special election set, Christie will not have his appointee of choice in the Senate for a full 18-month span. However, the governor ensured that a high-profile Democratic Senate candidate would not be running at the top of the ticket this November, when he and other Republicans are running in the main general election. Such a candidate on the ballot could help attract support to other Democrats running for lower-level office.
The Associated Press contributed to this report.